Another thing to be aware of is that to rack mount these servers, you will have to turn them through 90 degrees. As a result of this, the HDD's will rotate onto the flat plane rather than the vertical orientation they have been in up to this point.
As a result of this, we had the barings in one drive let go, and had to have the drive replaced.
Make sure you have a spare drive or a maintenance contract in place before rotating the server.
He's not the messiah, he's a very naughty boy (Monty Python's The Life of Brian)